Answer:
There are countless religions in the world, with most religions having sub-sects within them. Generally speaking, all religions attempt to help people make sense of their purpose and existence in this world, explain what occurs in the afterlife, and declare whether or not there is a deity, and if so, how we relate to this deity. The seven world religions in the list below comprise over 95% of the world's religious adherents. With each world religion is a link to a more detailed discussion of that religion's beliefs and practices.

Roman Catholicism and Christianity
There are approximately 1.2 billion professed Roman Catholics worldwide. Though the Roman Catholic Church has always been identified with Christianity, there are clear and fundamental differences between the two. Roman Catholics generally identify themselves as Christians, but for the purposes of distinguishing the two divisions of the Christian faith, adherents of Roman Catholicism are referred to as Catholics, while non-Catholic adherents of the Christian faith are referred to as Christians. There are approximately 900 million people worldwide who profess to be non-Catholic Christians. The name is derived from the fact that the early followers of Jesus of Nazareth were called Christians (Acts 11:26), which means literally “little Christs.” “Christ” is the Greek word for the Hebrew Messiah, the “anointed one.” Although Christians frequently identify with particular denominations such as Baptists, Methodists, Presbyterians, Lutherans, Pentecostals, and Nazarenes, they also universally claim the name Christian for themselves. Christianity is oftentimes collectively called “the church.” This is an indistinct term in that it is also the word used for local congregations and buildings as well as for specific denominations.

Islam
The name “Islam” literally means “submission,” and, as such, a Muslim is “one who submits to God.” Islam is based primarily on the writings of Mohammad, as recorded in the Qur'an. There are about 1.3 billion Muslims in the world today. Islam is represented all over the world. Though mostly associated with the Middle East, the largest Muslim populations are in Asia. Indonesia, Malaysia, Pakistan, Bangladesh, and India have sizable Muslim populations.

Hinduism
Hinduism is a word created by the Western world to encompass the dominant religious and social system of India. Traditionally, those we call Hindus refer to their religion as the “dharma,” which means “the way” or “the religion.” There are approximately 900 million Hindus in the world. Obviously, the greatest number of Hindus are located in India. Since Indians have emigrated all over the world, however, there are many Hindu communities in other countries. The total number of Hindus in India is subject to some controversy because it includes up to 300 million “untouchables” (dalits), who are officially counted as a part of the Hindu social structure but who are prevented from fully participating in Hinduism.

Buddhism
Buddhism is based on the teachings of the person called the Buddha, which means “enlightened one.” This religion has many different branches, but Buddhism is the only appropriate all-encompassing term, and its adherents, no matter how divergent in their beliefs, are happy to be known as Buddhists. Buddhism has about 360 million followers, placing it fourth, behind Christianity, Islam, and Hinduism. Buddhism originated in India. It is dominant in its more traditional forms in Sri Lanka and much of Southeast Asia (Thailand, Myanmar, Laos and Cambodia). Additionally, it has taken on various forms in many other Asian countries, most notably Tibet, Korea, China and Japan. Today Buddhism is frequently adapted and adopted by Westerners, though often at the expense of faithfulness to the traditional forms of this religion.

Judaism
The name “Judaism” comes from the tribe of Judah, one of the twelve ancient tribes of Israel. So, literally, it is the religion of those who come from the tribe of Judah, who are (in English) called the Jews. However, being Jewish refers to an ethnic identity as well as a faith, and nowadays there are many Jews who do not practice the Jewish faith, even though they are happy to be known as Jews ethnically and culturally. It is estimated that there are about 15 million religious Jews in the world today, but many of them do not practice any religion.

Baha’i
The term Baha'i literally means a “follower of Baha,” referring to Baha'ullah, the founder of the religion. Baha'i has more than seven million members. Originating in Iran, Baha’i is represented in well over 200 countries in the world, behind only Christianity (in over 250 countries), but far ahead of Islam, which is in about 175 countries.